检索结果-南通市图书馆

A Local Region Molecular Dynamics Simulation Method for Nanoscale Sliding Contacts

Chinese Journal of Mechanical Engineering 2018年第5期31卷 119-126页

作者： Rui-Ting Tong Geng liu tian-Xiang liu Shaanxi Engineering Laboratory for Transmissions and Controls Northwestern Polytechnical University Xi’an 710072 China Institute for Mechanics and Fluid Dynamics TU Bergakademie Freiberg Lampadiusstr. 4 09596 Freiberg Germany

Computational e ciency and accuracy always conflict with each other in molecular dynamics(MD) simulations. How to enhance the computational e ciency and keep accuracy at the same time is concerned by each corresponding researcher. However, most of the current studies focus on MD algorithms, and if the scale of MD model could be reduced, the algorithms would be more meaningful. A local region molecular dynamics(LRMD) simulation method which can meet these two factors concurrently in nanoscale sliding contacts is developed in this paper. Full MD simulation is used to simulate indentation process before sliding. A criterion called contribution of displacement is presented, which is used to determine the e ective local region in the MD model after indentation. By using the local region, nanoscale sliding contact between a rigid cylindrical tip and an elastic substrate is investigated. Two two?dimensional MD models are presented, and the friction forces from LRMD simulations agree well with that from full MD simulations, which testifies the e ectiveness of the LRMD simulation method for two?dimensional cases. A three?dimensional MD model for sliding contacts is developed then to show the validity of the LRMD simulation method further. Finally, a discussion is carried out by the principles of tribology. In the discussion, two two?dimensional full MD models are used to simulate the nanoscale sliding contact problems. The results indicate that original smaller model will induce higher equivalent scratching depth, and then results in higher friction forces, which will help to explain the mechanism how the LRMD simulation method works. This method can be used to reduce the scale of MD model in large scale simulations, and it will enhance the computational e ciency without losing accuracy during the simula?tion of nanoscale sliding contacts.

关键词： Local region molecular dynamics simulation Nanoscale Sliding contacts Contribution of displacement

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Martensitic transformation pathways and crystallographic orientation relationships in steel

引用

Journal of Materials Science & Technology 2024年第7期174卷 74-84页

作者： tian-Wei liu Xiao-Lei Wu State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

Martensite is one of the most important structures determining the ability to tailor the performance of steel and several other engineering *** previous studies,the face-centered cubic(FCC)to hexag-onal close-packed(HCP)(or body-centered cubic(BCC))martensitic transformation and the FCC to body-centered tetragonal(BCT)(or BCC)martensitic transformation during deformation and quenching were widely investigated;these transformations usually improve the plasticity and strength of steel,*** this work,detailed transmission electron microscopy(TEM)observations and electron diffraction pattern analyses of the BCT and BCC twins are performed along the[110],[131],and[¯153]zone *** transformation of BCT twins into BCC twins along the[131]zone axis is also analyzed through in situ heating during the TEM *** high-resolution TEM observations of mutually perpendicular BCT variants are consistent with the atomic arrangement obtained for the quenching pathway during the martensitic *** addition,different orientation relationships between austenite and marten-site are explained in terms of the atomic migration occurring during the deformation pathway and the quenching pathway of the martensitic transformation.

关键词： Body-centered tetragonal twin Martensitic transformation Steel Transmission electron microscopy Orientation relationship

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

A Note on Closeness between NP-Hard Sets and C=P

引用

Journal of Computer Science & Technology 2000年第2期15卷 194-195页

作者：刘田 Department of Computer Science and Technology Peking University Beijing P.R. China

Two sets are close if their symmetric difference is a sparse set. It is shown that NP-hard sets are not C=P-close unless NP C=C=P. This improves the previous result and has implication in quantum compulation.

关键词： NP-hard exact counting closeness quantum computation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Decode protein-metabolite regulatory network: one MIDAS at a time

引用

Signal Transduction and Targeted Therapy 2023年第9期8卷 3896-3898页

作者： tian liu Chen Gao Department of Pharmacology and Systems Physiology University of CincinnatiCincinnatiOHUSA

In a recent study published in Science,Hicks et *** Mass spectrometry integrated with equilibrium dialysis for the discovery of allostery systematically(MIDAS)to explore protein-metabolite interactome and have revealed previously unknown regulation for lactate dehydrogenase.1 This report brings an exciting new approach to address a long-standing challenge in *** functions are orchestrated by an interactive network of molecular constituents,the physical interactions between proteins and other molecular entities,such as DNA,RNA,and *** basic vocabulary for the book of life,these interactions are the fundamental mechanisms for complex physiology and diseases.

关键词： network such she

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Synthesis and characterization of novel calix[6]phyrin derivatives

引用

Chinese Chemical Letters 2008年第10期19卷 1199-1201页

作者： Wei Chen tian Jun liu Institute of Biomedical Engineering Chinese Academy of Medical Sciences Tianjin 300192 China

Three novel calix[6]phyrin derivatives have been synthesized by reaction of corresponding tripyrrane with aromatic aldehyde. The reaction condition was optimized and the structures of these compounds have been charact... 详细信息

关键词： Calixphyrin Synthesis Effect of catalysts

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Cloning, expression and biocharacterization of OfCht5, the chitinase from the insect Ostrinia furnacalis

引用

Insect Science 2013年第2期20卷 147-157页

作者： Qingyue Wu tian liu Qing Yang Department of Bioscience and Biotechnology Dalian University of Technology Dafian China

Chitinase catalyzes β,4-glycosidic linkages in chitin and has attracted re- search interest due to it being a potential pesticide target and an enzymatic tool for preparation of N-acetyl-β D-glucosamine. An individual insect contains multiple genes encoding chitinases, which vary in domain architectures, expression patterns, physiological roles and biochemical properties. Herein, Of ChtS, the glycoside hydrolase family 18 chiti- nase from the widespread lepidopteran pest Ostrinia furnacalis, was cloned, expressed in the yeast Pichia pastoris and biochemically characterized in an attempt to facilitate both pest control and biomaterial preparation. Complementary DNA sequence analysis indicated that Of CHT5 consisted of an open reading frame of 1 665-bp nucleotides. Phy- logenic analysis suggested Of Cht5 belongs to the Group I insect chitinases. Expression of Of Cht5 in Pichia pastoris resulted in highest specific activity after 120 h of induction with methanol. Through two steps of purification, consisting of ammonium sulfate pre- cipitation and metal chelating chromatography, about 7 mg of the recombinant Of Cht5 was purified to homogeneity from 1 L culture supernatant. Of Cht5 effectively converted colloidal chitin into chitobiose, but had relatively low activity toward a-chitin. When chi- tooligosaccharides [（GlcNAc）n, n = 3-6] were used as substrates, Of Cht5 was observed to possess the highest catalytic efficiency parameter toward （GlcNAc）4 and predominan- tely hydrolyzed the second glycosidic bond from the non-reducing end. Together with fl-N-acetyl-D-hexosaminidase OfHexl, Of Cht5 achieved its highest efficiency in chitin degradation that yielded N-acetyl-β D-glucosamine, a valuable pharmacological reagent and food supplement, within a molar concentration ratio of Of Cht5 versus Of Hexl in the range of 9 ： 1-15 ： 1. This work provides an alternative to existing preparation of chitinase for pesticides and other applications.

关键词： chitin chitinase glycoside hydrolase N-acetyl-β-D-glucosamine Ostriniafurnacalis pest control

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Effect of hot isostatic pressing processing parameters on microstructure and properties of Ti60 high temperature titanium alloy

引用

China Foundry 2023年第1期20卷 49-56页

作者： tian-yu liu Kun Shi Jun Zhao Shi-bing liu You-wei Zhang Hong-yu liu tian-yi liu Xiao-ming Chen Xin-min Mei Shenyang Research Institute of Foundry Co. Ltd.Shenyang 110022China State Key Laboratory of Light Alloy Casting Technology for High-end Equipment Shenyang 110022China

Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in *** order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in *** show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 *** higher temperature and pressure can improve the microstructure ***,the higher pressure can promote the composition *** the temperature increases from 880℃to 960℃,α-laths are *** with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are *** tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.

关键词： hot isostatic pressing processing parameters Ti60 titanium alloy defects composition uniformity microstructure mechanical properties

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Position-Aware and Subgraph Enhanced Dynamic Graph Contrastive Learning on Discrete-Time Dynamic Graph

引用

Computers, Materials & Continua 2024年第11期81卷 2895-2909页

作者： Jian Feng tian liu Cailing Du College of Computer Science&Technology Xi’an University of Science and TechnologyXi’an710054China

Unsupervised learning methods such as graph contrastive learning have been used for dynamic graph represen-tation learning to eliminate the dependence of ***,existing studies neglect positional information when learning discrete snapshots,resulting in insufficient network topology *** the same time,due to the lack of appropriate data augmentation methods,it is difficult to capture the evolving patterns of the network *** address the above problems,a position-aware and subgraph enhanced dynamic graph contrastive learning method is proposed for discrete-time dynamic ***,the global snapshot is built based on the historical snapshots to express the stable pattern of the dynamic graph,and the random walk is used to obtain the position representation by learning the positional information of the ***,a new data augmentation method is carried out from the perspectives of short-term changes and long-term stable structures of dynamic ***,subgraph sampling based on snapshots and global snapshots is used to obtain two structural augmentation views,and node structures and evolving patterns are learned by combining graph neural network,gated recurrent unit,and attention ***,the quality of node representation is improved by combining the contrastive learning between different structural augmentation views and between the two representations of structure and *** results on four real datasets show that the performance of the proposed method is better than the existing unsupervised methods,and it is more competitive than the supervised learning method under a semi-supervised setting.

关键词： Dynamic graph representation learning graph contrastive learning structure representation position representation evolving pattern

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

POLY(MALEIC ANHYDRIDE-CO-ACRYLIC ACID)/POLY(ETHYLENE GLYCOL)HYDROGELS WITH pH- AND IONIC-STRENGTH-RESPONSES

引用

Chinese Journal of Polymer Science 2010年第6期28卷 951-959页

作者： Meng Yang Bo-tian liu Ge Gao Xiao-li liu Feng-qi liu College of Chemistry and Macdiarmid Laboratory Jilin University Changchun 130012 China

Poly（maleic anhydride-coacrylic acid）,P（MA-AA）,was synthesized by the free-radical copolymerization of maleic anhydride with acrylic acid,and fast responsive pH-sensitive poly（maleic anhydride-co-acrylic acid）/polyethylene glycol,P（MA-AA）/PEG,hydrogels were prepared using PEG as macromolecular cross-linking ***-IR and ~1H-NMR spectrometry were applied to characterize the structure of P（MA-AA）.The influences of pH and ionic strength on the swelling behavior of P（MA-AA）/PEG hydrogels and the swelling-deswelling changes along with the repeated changes between acid and alkali conditions were *** results showed that there was a hundredfold difference in the swelling ratios between the conditions of acid and alkali,and the swelling capability could not be weakened after multiple swelling-deswelling *** results of swelling kinetics demonstrated that the response rate of P（MA-AA）/PEG hydrogels was very fast,because the swelling transition points always occurred at 10 *** pH-responsive hydrogels reported here might be a smart material for potentially applications in many areas,including biosensors,drug-delivery devices and tissue engineering.

关键词： pH-response P(MA-AA) Macromolecular cross-linking agent External cross-linking

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Some Structural Properties of SAT

引用

Journal of Computer Science & Technology 2000年第5期15卷 439-444页

作者：刘田 Department of Computer Science and Technology Peking University Beijing P.R. China

The following four conjectures about structural properties of SAT are studied in this paper. (1) SAT ∈ PSPARSEnNP; (2) SAT ∈ SRTDtt; (3) SAT ∈ PttbAPP; (4) FPttSAT = FPlogSAT. It is proved that some pairs of these conjectures imply P = NP, for example, if SAT E pSPARsEnNP and SAT 6 PttbAPP, or if SAT E SRTDtt and SAT E PttbAPP, then P = NP. This improves previous results in literature.

关键词： structural complexity SAT sparse set approximable set truthtable reduction non-adaptive search reducible to decision.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：